1. Field of the Invention
The present invention relates generally to composite spring seats for shock absorbers, and more specifically, to impact reinforced composite spring seats for shock absorbers.
2. Description of the Related Art
Strut-type suspension systems are well known in the motor vehicle industry. A telescopic strut assembly normally incorporating a hydraulic damper is used as one of the locating members for a wheel of a motor vehicle. The most common form of a strut-type suspension is the MacPherson strut suspension system. The MacPherson strut assembly includes a coil spring located concentrically around the telescopic strut which is a shock absorber. The upper end of the MacPherson strut assembly includes a top mount assembly which is mounted to the vehicle body. These shock absorbers known in the related art typically include an outer tube, a piston, a rod, fluid, and one or more valves, whereby the piston is connected to the rod and travels within fluid in the outer tube in operation so as to dampen axial movement of the rod with respect to the outer tube.
The coil spring is located around the shock absorber and it extends between an upper spring seat which is a part of the top mount assembly and a lower spring seat which is attached, typically by welding, to the shock absorber of the strut assembly. The spring seats of the strut assembly have several functions for the suspension system. The spring seats support and maintain the correct position of the spring and support the loading on the spring under all driving conditions of the vehicle for the entire life of the vehicle.
The spring seats are supposed to be mechanically resistant during the life of the vehicle and resist braking loads, deformations, wear, abrasion, changing loads and hits by stones and other debris. The spring seats are also supposed to be environmental and corrosion resistant to different temperatures, different moisture levels, aggressive liquids and gases. The spring seats are supposed to ensure proper fixing of the components of the strut assembly, easy assembly of the strut assembly into the vehicle and with the other components of the strut assembly they resist any unwanted displacements and/or rotations. The design of the spring seats also ensures that the spring to spring seat contact does not promote or accelerate corrosion of the spring or the spring seat.
The related art lower spring seats were traditionally formed of a single piece of stamped or formed metal component. The single piece lower spring seat includes an annular disc defining an opening that supports the lower end of the spring and a tubular extension about the opening which extends from the annular disc. The tubular extension is designed to be welded or otherwise attached to the outer tube of the shock absorber.
It is a goal of the automotive industry to reduce the weight of vehicles and remove any unnecessary weight from components forming the vehicle. As one example, attempts have been made to manufacture the spring seats (as well strut assemblies themselves) from composite materials. When the spring seats are formed of composite materials, it is a challenge to have a sufficiently strong and stiff design with very limited creep. It is also necessary for the composite spring seat to be able to dissipate energy in case of spring failure. Attempts have been made to increase the thickness of the composite materials to give improved strength, but these attempts have not been successful due to the cost of the additional material. Further, the performance of the composite spring seats has to be able to withstand significant temperature differences, such as extreme heat and extreme cold. When the composite spring seats are exposed to extreme cold, the spring seats can become brittle and crack or shatter in case of spring impact. When the spring seats crack or shatter, the forces from the spring cause the spring seat to disengage from the shock absorber which can cause dangerous situations.
Another approach that has been utilized to accommodate forces on composite spring seats employs a steel or rubber pad positioned on the entire surface of the spring seat. The pad would absorb energy in case of spring failure. However, it is costly to have to use a pad to cover the entire spring seat. These related art composite spring seats and different approaches exhibit undesirable failure modes that can lead to dangerous and hazardous conditions when operating a vehicle that are not desirable.